I had linoleum ;put into a bathroom and the toilet reseated. Since thenn a black stain has been growing around the toilet and under the flooring. It is not on top of the flooring and that toilet is on a slab and sees little use .
The job is going to have to be redone but it would help to know what the problem is. Again, the toilet is well sealed to the flooring and both the toilet and the flooring is new and the stain us under the flooring but showing through and looking like it is on top. There is never water on the flooror anything else that could work its way down from the top.